The field of the invention pertains to the transmission of power by means of belt driven pulleys and, in particular, to variable speed pulleys wherein the effective pulley diameter is infinitely variable.
A variety of variable speed pulleys have been developed previously with a variety of mechanisms for changing the effective diameters of the pulleys. U.S. Pat. No. 2,013,268 discloses an early pulley having interleaved sheaves urged together by springs to either side of the sheaves. The sheaves are slideably keyed to a sleeve in turn mounted on a shaft.
U.S. Pat. No. 2,120,383 discloses an early pulley wherein the sheaves are double keyed to the shaft. The keys also act as part of the actuator along with a pair of radial lever arms to move the sheaves apart. U.S. Pat. No. 2,107,483 discloses an early pulley with the sheaves almost fully interleaved and press fit onto overlapping sleeves. The sleeves in turn are axially slideable on the shaft. U.S. Pat. No. 2,152,207 discloses a pulley with sheaves almost fully interleaved and urged together by springs to either side. All of the above variable diameter pulleys are self actuating in the sense that belt tension on the pulley opposes the axial spring force and causes the sheaves to separate thereby decreasing the pulley effective diameter.
U.S. Pat. No. 2,210,300 discloses an early application of the variable speed pulley to a machine wherein a mechanical external actuator causes one interleaved sheave to be moved axially relative to the other sheave thereby changing the effective pulley diameter. More recently U.S. Pat. No. 4,398,899 discloses a mechanically actuated interleaved pulley wherein one pulley hub comprises interleaved extensions of the leaves or tangs of both pulley sheaves. The interleaved extensions, however, are spaced radially from the shaft by a solid portion of the sheave hub and the extensions of one sheave slide relative to the extensions of the other sheave on the hub.
The variable effective diameter pulleys discussed above are generally of relatively heavy construction for industrial power transmission purposes with the exception of the last patent which is directed to very light duty applications such as the transmission of power for a self-propelled walk behind lawn mower. Neither above approach is particularly suited to automotive applications where very long pulley and belt life and inexpensive manufacture and assembly become very important considerations. For reasons of fuel economy and extended lifetime it would be desirable to operate alternators, power steering pumps and air conditioner compressors at a substantially constant speed regardless of engine speed. Therefore, a suitable variable effective diameter pulley for automotive engine applications would enjoy wide use.